In general untreated meat products rapidly become pale and/or spoil due to oxidation of the muscle pigment as a result of contamination with undesirable microorganisms which may be a health hazard and are introduced during the slaughter operation in particular or during further processing of the foodstuff. Curing delays or suppresses these deleterious effects through a number of parallel mechanisms: microorganisms are prevented from proliferating, excess water is withdrawn, which improves the consistency and lowers the aW value and the curing color and a typical curing aroma are formed.
Nitrite curing salt (NPS) is a composition of nitrite salt (usually NaNO2) and table salt (NaCl) which is known for use in curing foods, for example raw cured products and raw sausage. In the so-called reddening transfer process, nitrite is disproportionated to nitrate and nitrogen monoxide (NO) under acid catalysis. NO then binds to the myoglobin which is present in the muscle fibers of muscle meat of higher vertebrates, to form a red pigment, nitrosomyoglobin which can impart a permanent red pigmentation to foodstuffs.
Another component of the curing process is the enzymatic activity of microorganisms present in the foodstuff or optionally added in a targeted manner, especially staphylococci and lactobacilli. These organisms serve to convert nitrate back into nitrite through a nitrate reductase activity inherent in the organism, and cause a drop in pH (formation of acid) through their metabolic activity, which supports the disproportionation to NO. Disproportionation is further supported by anaerobic glycolysis which proceeds in the muscle meat and is associated with decline in pH (formation of acid). The decline in pH causes coagulation of the protein of the foodstuff, in particular the muscle protein, which thus becomes more easily cuttable.
By heating at the end of the curing process, nitrite reacts with a certain other component of the foodstuff so that additional substances with an antimicrobial action, the so-called Perigo factor, are formed. On the whole a much larger amount of nitrite is necessary for the preservative antimicrobial effect than for the development of curing color and curing aroma.
Nitrite as such is known as a toxic substance which can interfere with the metabolic processes in the human or animal body in a deleterious manner, in particular parts of the respiratory chain. Although foodstuffs cured with nitrite, in particular cured meat products, make only a very minor contribution of approx. 3% to the total nitrite burden in the human body, it is still desirable and necessary from the standpoint of medical physiology, from the standpoint of the “informed” consumer, for the declaration of ingredients on food products and also to fulfill new statutory requirements to reduce the use of nitrite in foodstuffs to be cured and in particular to reduce the residual nitrite content in a cured food product. Thus, the new guideline values for the addition of nitrite salts to cured and dried, meat products that have not been treated with heat include 150 mg/kg (expressed as NaNO2) for the maximum addition of nitrite to the foodstuff to be cured and 50 mg/kg for the maximum residual nitrite level in the cured food product at the time of transfer to the consumer. For the stricter European ecological guidelines, limit values of 80 to 100 mg/kg apply for the maximum addition of nitrite and a maximum allowed residual nitrite content of 50 mg/kg at the time of transfer to the consumer. These values may not be met in some known processes if the shortcomings in the curing result associated with this such as inadequate reddening which is not permanent, taste disadvantages, low stability and microbial contamination.
To improve the desired curing effect of nitrite salts, in particular the microbial stabilization and the red color and also to maintain these even with small quantities of nitrite, so-called curing aids are known to be added during the curing process. A known curing aid is ascorbic acid or ascorbate which is used as a reducing agent having an antioxidant effect and also as an acid-forming component, optionally in combination with sodium tripolyphosphate or synthetic antioxidants such as BHA and BHT. Furthermore, spices or spice extracts which contain naturally occurring antioxidant may also be used. These include, for example, such spices as cloves and rosemary as well as extracts thereof. These curing additives have a recognizably negative effect on taste in certain recipes. Furthermore, the addition of these substances is associated with changes in the sampling sequence in comparison with traditional recipes.
In other approaches an attempt is made to improve the curing results and to bypass statutory restrictions with respect to the addition of nitrate or nitrite salts by adding vegetable concentrates with a high nitrate content to the foodstuff. A low nitrate or nitrite content is then usually only seemingly achieved. Additional curing additives include “sugar substances” which are used to support the curing process and are supposed to improve the curing results. Known sugar substances serve as a nutrient source for the microorganisms (curing flora) which are present in the curing process.
The reddening process to form the permanent meat color in the curing process is known to be time-consuming and the recommended reduced nitrite levels lead to a reddening which unfortunately lasts only a relatively short amount of time. It is therefore desirable to accelerate the reddening process and/or improve the reddening result even with a short process time and a lower nitrite content.
The technical problem on which the invention is based is to provide improved methods and agents for curing foods with which the residual nitrite content in the cured food can be reduced and/or the quality of the curing result, in particular the reddening, especially the intensity and stability of the curing color can be improved.